The present invention relates to a carburetor arrangement for an internal combustion engine of a manually guided implement, and includes a carburetor that is in particular embodied as a diaphragm carburetor.
Manually-guided implements such as power chain saws, brush cutters, trimmers, vacuum or blower devices, or the like are provided with a carburetor for producing a fuel/air mixture. For this purpose, a number of fuel nozzles are provided in an air channel of the carburetor that leads to the internal combustion engine; fuel enters the air channel through the fuel nozzles. The fuel nozzles, generally a main nozzle and an idling nozzle, are dimensioned with respect to their flow volume such that in an at least approximately steady operation of the internal combustion engine, a fuel/air mixture results having a desired fuel/air ratio. During the sudden opening of a butterfly valve that is provided for controlling the power, there often occurs a leaner mixture, which prevents a powerful acceleration of the internal combustion engine.
To compensate for the so-called acceleration deficit as a consequence of the leaner mixture, carburetor arrangements are known that have an accelerator pump. By means of the accelerator pump, during the rapid opening of the butterfly valve an additional quantity of fuel is injected into the air channel, thereby temporarily increasing the fuel portion in the fuel/air mixture. Known accelerator pumps comprise an accelerator piston that is guided in a pump chamber, is movably coupled with the butterfly valve, and during the opening of the butterfly valve conveys into the air channel a quantity of fuel that was stored in the pump chamber. The filling of the pump chamber with fuel is effected via a pump line, the opening of which into the pump chamber is partially opened, or closed, via the operating path of the accelerator piston. In this connection, the accelerator piston operates as a path-controlled feed valve. Such an arrangement leads to a relatively low intake and hence supply quantity of fuel per pump process relative to the volume of the pump chamber. Thus, the accelerator pump must be made appropriately large. For the opening and closing of the opening-out of the pump line, a dead path of the accelerator piston is necessary, as a consequence of which the accelerator injection process commences only after a time delay, i.e. after a certain opening angle of the butterfly valve.
It is therefore an object of the present invention to provide a carburetor arrangement, the accelerator pump of which has an improved effect.